Terrible Advice Tuesdays (T.A.Tues): Schedule 20 PVC won’t work for plumbing a saltwater tank due to the pressure in the lines.

The rest of the story: For those of you who don’t know, the higher schedule number (20, 40, 80), the greater the wall thickness of the pipe. The argument here is that schedule 20 PVC is so thin walled that it will fail under the demands of a saltwater tank.

Let’s set the record straight on a couple of things to start:

The pressure (psi) inside your drain lines is nearly zero, assuming you aren’t flooding the lines completely. Even if you flood the drain completely, the psi is still really low.

Even though your return lines are pressurized, the pressure in them is still low.

Schedule 20 PVC pipe is rated up to 200 psi which is WAY more than you’ll need for your tank.

Ok, so what about smashing through schedule 20 pipe. It is thinner than schedule 40 right?

Yes!

That being said, I’ve accidentally hit schedule 20 PVC pipes on saltwater tanks with protein skimmer cups, return pumps, and various tools and never broken through a pipe. And if you are breaking the pipes on your tank, you either have serious anger management issues, or you are trying to do something with the pipe that it wasn’t designed for.

Given those facts, it is really easy to see why the advice that “schedule 20 PVC won’t work on a saltwater tank” is horrible advice.

For the record, I frequently use schedule 20 PVC pipe on my tank builds and I’ve never had a problem with it.